Method of forming conical shells



y N. MICHELMAN 2,248, 78

METHOD OF FQRMING CONICAL SHELLS v Filed Nov. 4, 1938 6 I I3 I3 I! '3Fig ,4,

Patented July 8, 1941 *UN-ETED STATES, PATENT *OFFI'CE 2,248,278? HMETHOD or FoRMINGooNrcAL SHELLS Nathan Michelman, Bathe. N. Y.Application November 4, 1938, Serial'No. 238,882 (or. 29 1'55 q 1 Claim.

This invention relates to. improvements in methods of and apparatus forforming conical ratus, and operations, particularly when a series ofconnected conical shells of gradually decreasing size are required. Thesecond of these methods is deficient in that considerable effort isrequired in the pressing or bending operation to bring the edges of theV'-slit in the tube into abutment, particularly towards the end havingthe greatest slit width, usually resulting in a distending or flatteningof the shell at the zones adjacent and at the slit edges. Further, inthis second method, the welding operation along the resultinglongitudinal slit line defined by the slit edges, causes an arcuatelongitudinal bending of the formed shell requiring a re-heating andrepressing or bending of the shell after the welding step to impart therequired conical formation.

To obviate these difiiculties and to provide a generally equaldistribution of the stresses upon a slit cylindrical shell in thepressing or bending thereof to form a conical column, I have formed anexcision in the nature of a slit of gradually decreasing width, but havemade the excision of helical or spiral form as it progressesperipherally from end to end of the cylindrical shell. By this slitformation I am enabled in the subsequent pressing or bending operationto provide for a balanced stress or pressure along the length andperiphery of the slit cylindrical shell, so that the resulting conicalshell will be substantially arouate with respect to its peripheralcontour.

These and other advantages, capabilities and features of the inventionwill appear from the subjoined detailed description of one specificembodiment thereof illustrated in the accompanying drawing, in whichFigure 1 is a front view of a cylindrical shell excised in accordancewith my invention.

Figure 2 is a front view of the excised cylindrical shell after swagingin accordance with my invention.

Figure *3 is a perspective front elevation of my swaging'frame,

Figure 4 is an end-elevation partly in section of asection'at one end ofmy swaging frame in application.

Figure 5 is an end elevation partly in section of another section at theother end of my swaging frame in application.

' Referring to thereference characters in the drawing, letter Arepresents a stock cylindrical shell, excised from end to end to form ahelicoidal slit ill of gradually decreasing width, and letter Brepresents the excised shell of Figure 1 after swaging to provide afrusto-conical shell with the edges of the excision brought intoabutting relationship asat II, and after welding to form 'a sealedenclosing unit.

' The pressing or swaging apparatus comprises a framework C, formedof aseries of plates 12 spacedly mounted along frame rods iii. The plates l2have a polygonal outer periphery l4 and are centrally apertured todefine an inner periphery l5. The frame rods l3 pass through aperturesin plates l2 in the line of the apices of the outer periphery of theplates.

In the framework, a plurality of plates [2a disposed preferably one ateach end and one centrally thereof, are provided for service asguideways for the press rods 16. These plates l2a have the same outerperipheral contour but are wider than plates l2, their central aperturebeing of lesser diameter than that of plates l2. The plates 12a. haveformed along their inner periphery I5a spaced right angular guidegrooves l1, opposite to and in line with the frame rods B. The pressbars I6 which are rectangular in crosssection extend along the length ofthe framework and rest in and are guided for longitudinal movement inassembling the framework, and. transverse movement intheir pressingaction by the side walls of the grooves IT. The grooves H are of suchdepth that their closed ends are in line with the inner peripheralsurface l5 of the plates l2, so that the press bars I6 when set Withinthe grooves I! of plates I20, rest against the inner peripheral surfaceI5 of the plates l2. The innermost central aperture of the framework asdefined by the press bars l6 extending inwardly of the plates Hat is ofsufficient diameter to permit insertion of the slit cylindrical shellshown in Figure 1.

To bring the edges of the excised slit it! of the cylindrical shell A ofFigure 1 into abutting relationship indicated as l l in Figure 2, thefollowing steps are followed: a

The framework C is disposed preferably horizontally to rest on one ofthe polygonal outer peripheral faces of the plates l2 and [2a, and thepress bars I6 removed from the grooves ll of the plates IN. The slitcylindrical shell A is inserted in the framework and successively therespective press bars are slid to extend longitudinally into theframework, being disposed within the guide grooves I! of plates I2a andadapted to rest adjacent the periphery of the slit shell, the frameworkbeing rotated until all the press bars are in position, therebyproviding spaced longitudinal action zones forthe same with respect tothe slit cylindrical shell. A series of wedges l8 are inserted in spacedrelationship along the respective lengths of the framework betweenopposing frame rods I3 and press bars it, such wedges being disposedoneor more between each set of plates I2 or [2 and In. The wedges arethen driven in the direction of the arrow as the framework isperiodically rotated to rest on the respective polygonal faces of thespaced plates I2 and l2a, so as to provide a gradual pressing andbending effect upon the slit cylindrical shell along the longitudinalzones defined along the length of the press bars, which as they aredisplaced inwardly from their grooves away from the fixed frame rods arecaused to press against the peripheral surface of the slit cylindricalshell. progressively along their length away from the frame rods ingreater amounts, corresponding t the original wider dimensions of theexcision slit being closed, the relative relationship of the press barsI6 and the frame rods l3 at the con- The press bars are displaced suchfigures the narrow end of the frusto-conlcal shell is formed, and Figure5, where the wider end is formed.

Since the pressing or swaging is carried out by a progressive driving ofthe wedges along longitudinal zones of the framework as the same isperiodically rotated, a gradual pressure and even stress is appliedlongitudinally of the tubular slit shell as it is brought to the desiredfrusto-conical contour, at which time the edges of the slit are inabutment to provide the conformation shown in Figure 2.

When the edges of the slit are brought into abutment the shell is weldedwhile in the frame to substantially seal the slit defined by theabutting edges. The wedges are then driven out, the frusto-conical shellremoved from the frame and those sections of the slit abutting edgesunavailable for welding by virtue of the proximity of the innerperipheries of the pltaes I2 and I2a are welded to complete the closurealong the abutting edges of the helicoidal slit line of thefrusto-conical shell shaped in the framework.

It is obvious that various changes and modifications may be made to thedetails of construction without departing from the general spirit of theinvention as set forth in the appended claim.

'I claim:

The method of forming a conical shell from a cylindrical shell, whichconsists in excising the cylindrical shell to form a helical slit ofgradually decreasing Width from end to end of the cylindrical shell,thereafter applying pressure to the cylindrical shell at a plurality ofzones to bring the edges of the shell defined by the slit into abutmentand thereafter welding the abutting edges to each other.

NATHAN MICHELMAN.

